Is a properly sized three-wire dryer cord and receptacle acceptable as the disconnecting means for an electric water heater in a dwelling unit?

This appears to be a misuse of flexible cord. Flexible cords are permitted on appliances that qualify under Section 422.16. The basic requirements for permission to use cord and plug connections are given in part (A) and state, “Flexible cord shall be permitted (1) for the connection of appliances to facilitate their frequent interchange or to prevent the transmission of noise or vibration or (2) to facilitate the removal or disconnection of appliances that are fastened in place where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance or repair and the appliance is intended or identified for flexible cord connection.”

The disconnecting means for a permanently connected water heater must comply with 422.31(B). This part requires a disconnecting means within sight of the water heater, or if more than 50 feet from the appliance, it must be capable of being locked in the off position. If more than 50 feet away, the locking means must remain at the disconnect whether a lock is installed on the water heater or not.

Commercial kitchen GFCIs

I have a job to install an isolated ground receptacle in the kitchen of a restaurant. The receptacle will be about 8 feet above the floor and will supply an information monitor. Is a ground-fault circuit interrupter (GFCI) required for this receptacle? Does any manufacturer provide an isolated ground GFCI receptacle?

Section 210.8(B)(5) requires GFCI protection for all 15- and 20-ampere, 125-volt receptacles in kitchens in other than dwelling units. Since there is no maximum height for these receptacles, a receptacle located 8 feet above the floor of a commercial kitchen requires GFCI protection.

I do not know of any manufacturer that makes an isolated GFCI receptacle. However, an isolated ground receptacle can be supplied from a GFCI circuit breaker or a GFCI receptacle.

Type NM cable installed outdoors

An air conditioning unit is installed outdoors where it is subjected to the weather. Does the National Electrical Code (NEC) permit Type NM cable in flexible metal conduit for this installation? If this cannot be done, is type NM cable in electrical metallic tubing acceptable?

The answer to both questions is no. Where the wiring method is exposed to the weather, it is considered to be in a wet location. This section was added to the 2008 edition of the NEC and makes it clear that the interior of raceways installed outdoors are wet locations. The section number is 300.9 and states, “Raceways in Wet Locations Above Grade. Where raceways are installed in wet locations above grade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations above grade shall comply with 310.8(C).”

Based on the addition to this section and the information in 334.12(B)(4), which prohibits nonmetallic-sheathed cable in wet or damp locations, this cable cannot be used for this application.

Sizing grounding-electrode conductors

What size grounding-electrode conductor is required for three-phase, four-wire, 120/240-volt delta service? The A and C phases are 500 kcmil Type THWN copper conductors and the B phase is 3/0 Type THWN copper. The lighting load is 200 amperes at 120/240 volts single-phase, and the motor load is 150 amperes, three-phase.

To comply with 250.24(C)(1), the grounded conductor for this three-phase, four-wire delta service must have a grounded conductor with an ampacity of not less than that of the ungrounded service conductors. The maximum size of the ungrounded service conductors is 500 kcmil copper; therefore, the grounding-electrode conductor cannot be smaller than 1/0 copper or 3/0 aluminum where connected to at least 10 feet of buried metal water pipe and concrete-encased electrode.

The phase conductor having the higher voltage to ground on a three-phase, four-wire delta system must be connected to the B phase in the service equipment where the phase arrangement is A, B and C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard or panelboard. An exception allows the conductor with the higher voltage to ground to occupy a different position when the switchboard or panelboard is in the same section as the metering equipment. This requirement is in 408.3(E). Part (F) of the same section requires that the high leg be identified by a permanent plaque that reads, “Caution _____ Phase Has _____ Volts to Ground,” where it is necessary to fill in the correct phase amount of volts that are grounded.

The color of this conductor with the higher voltage to ground is orange or is identified by other effective means. This identification is required at each point on the system where a connection is made if the grounded conductor also is present. This requirement is in 110.15.

GFCI protection for receptacles

A commercial building is under construction, and the electrical contractor has decided to provide signs that reads, “If you use this receptacle, you must provide your own GFCI protection.” Is this considered a Code-compliant installation?

Yes it is. The words in 590.6(A) do not require that 15-, 20- and 30-ampere, 125-volt receptacles be GFCI protected. Part of 590.6(A) reads, “For the purposes of this section cord sets or devices incorporating listed ground-fault circuit-interrupter protection for personnel identified for portable use shall be permitted.”

Although it was not clear in the 2005 edition of the NEC, some electrical inspectors and authorities having jurisdiction (AHJ) required AFCI protection for outlets in bedroom clothes closets. This changed in 210.12(B) in the 2008 edition: “Dwelling Units. All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms shall be protected by a listed arc-fault circuit interrupter, combination type, installed to provide protection of the branch circuit.” Notice that a combination type AFCI is required for all these locations.

Hydromassage bathtub branch circuit

I have always complied with the Code by installing a dedicated 20-ampere branch circuit in the bathroom to supply all the items in the bathroom including a hydromassage bathtub. The electrical inspector is now requiring a dedicated branch circuit for the hydromassage bathtub plus an additional branch circuit for other electrical equipment. Is this a requirement in the 2008 edition of the NEC?

Yes it is. In 210.11(C)(3) the Code requires a 20-ampere branch circuit to supply bathroom receptacles. This branch circuit cannot have any other outlets. And 680.71 in the 2008 edition of the NEC requires hydromassage bathtubs and their associated electrical components to be supplied by an individual branch circuit and protected by a readily accessible GFCI. Also, all 125-volt, single-phase receptacles not exceeding 30-amperes located within 6 feet measured horizontally from the inside walls of the hydromassage bathtub must be protected by GFCIs.

Article 100 defines an individual branch circuit as a “branch circuit that supplies only one utilization equipment.”

Conductor derating for stapled together nonmetallic sheathed cables

Where two 12/2 with ground nonmetallic sheathed cables are stapled together for the kitchen appliance branch circuits on wood studs and a 3-inch thick fiberglass insulation blanket is installed around the conductors, what, if any, derating factors apply?

No derating is required for these conductors where two cables are secured to a framing member with a single staple. Also, there is no derating required where NM cables are in thermal insulation. Where three or more NM cables are installed without maintaining spacing and pass through a hole in a wood framing member that is fire- or draft-stopped, the allowable conductor ampacity must be adjusted to comply with 334.80. There also are requirements that are general in nature for derating conductors in 310.10.

GFCIs on three-wire branch circuits

Does the NEC permit three-wire, 12 AWG copper conductors in NM cable to supply the two small appliance branch circuits protected by GFCI receptacles?

The National Electrical Code is silent on this subject, but GFCIs cannot be used on three-wire, 120/240-volt branch circuits that share the neutral conductor. Where both ungrounded conductors of the three-wire branch circuit cause an unbalanced current flow in the neutral conductor, the GFCIs trip when the neutral current does not equal the current in the ungrounded conductor and the difference is more than 6 milliamperes.

FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.

George W. Flach was a regular contributing Code editor for Electrical Contractor magazine, serving for more than 40 years. His long-running column, Code Q&A, is one of the most widely read in the magazine's history. He is a former chief electrical in...

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This is the third article of the series reviewing the most popular questions that have appeared in NECA’s online Code Question of the Day and have generated the most comments from subscribers. All answers have been updated to comply with the 2008 National Electrical Code...Read the Article